The present invention relates to a method for the preparation of a shaped article of a crosslinked poly(vinylidene fluoride) resin. More particularly, the invention relates to a low-cost method for the industrial preparation of a shaped article of a crosslinked poly(vinylidene fluoride) resin, which is uniformly crosslinked to the depth of the core portion of the article and has greatly improved resistance against heat, water and chemicals.
It is known that poly(vinylidene fluoride) resins can be crosslinked by the irradiation with electron beams in a dose of several Mrad to several tens of Mrad in the absence or presence of a crosslinking aid to enhance the efficiency of the crosslinking reaction with an object to improve various properties of the shaped articles of the resin (see, for example, U.S. Pat. No. 3,269,862). This method by the electron beam irradiation is, however, disadvantageous, due to the high costs for the very expensive apparatus of electron beam irradiation and has a limitation in the applicability to thick-walled articles or articles of an irregular form due to the relatively small penetrability of electron beams through synthetic resin bodies.
Apart from poly(vinylidene fluoride) resins, Japanese Patent Publication 61-50484 teaches that certain halogen-containing synthetic resins, e.g., chlorinated polyethylenes, poly(vinyl chloride) resins, poly(vinylidene chloride) resins and the like, can be crosslinked by the reaction with a mercapto group-containing organosilane compound as a crosslinking agent. This method, however, is not applicable to poly(vinylidene fluoride) resins because the mercapto group containing organosilane compound acts as a dehydrofluorinating agent of the poly(vinylidene fluoride) resin to introduce ethylenically unsaturatred double bonds to the main chain structure of the polymer rather than to act as a crosslinking agent.